Systems and methods for electric track vehicle control

Abstract

Systems and methods for track vehicle control are provided. In one embodiment, a method comprises: receiving a steering control signal; inputting a first rotation signal from a first encoder representing a rotational frequency and phase of a first electric motor coupled to a first continuous track mechanism; inputting a second rotation signal from a second encoder representing a rotational frequency and phase of a second electric motor coupled to a second continuous track mechanism; and outputting motor control signals to a first and second motor controllers in response to the steering control signal and differences between the rotational frequency and phase for the first electric motor and the rotational frequency and phase for the second electric motor, wherein the first motor controller is coupled to the first electric motor and the second motor controller is coupled to the second electric motor.

What is claimed is: 
     
       1. A vehicle steering control system for a track vehicle, the system comprising:
 a first continuous track drive sub-system positioned on a first side of a track vehicle, the first continuous track drive sub-system comprising: a first continuous track mechanism, a first electric motor coupled to the first continuous track mechanism, a first motor controller coupled to the first electric motor, and a first rotation encoder coupled to the first electric motor; 
 a second continuous track drive sub-system positioned on a second side of a track vehicle, the second continuous track drive sub-system comprising: a second continuous track mechanism aligned parallel to the first continuous track mechanism, a second electric motor coupled to the second continuous track mechanism, a second motor controller coupled to the second electric, and a second rotation encoder coupled to the second electric motor; 
 a main controller configured to input a steering control signal; and 
 a phase and frequency decoder coupled to the first rotation encoder and the second rotation encoder, wherein the phase and frequency decoder inputs a first rotation signal from the first rotation encoder representing a rotational frequency and phase of the first electric motor, wherein the phase and frequency decoder inputs a second rotation signal from the second rotation encoder representing a rotational frequency and phase of the second electric motor; 
 wherein the main controller outputs motor control signals to the first motor controller and the second motor controller in response to the steering control signal and monitored differences between the first rotation signal and the second rotation signal to drive the monitored differences below a threshold. 
 
     
     
       2. The system of  claim 1 , wherein the first rotation encoder and the second rotation encoded comprise one of a sine encoder or an incremental encoder; and
 wherein the first rotation signal and the second rotation signal are complex signals. 
 
     
     
       3. The system of  claim 1 , wherein the first electric motor and the second electric motor are alternating current (AC) permanent magnet (PM) electric motors. 
     
     
       4. The system of  claim 3 , wherein the first electric motor and the second electric motor are 3-phase AC electric motors; and
 wherein the first motor controller and the second motor controller each comprise 3-phase DC-to-AC electric power inverters. 
 
     
     
       5. The system of  claim 1 , wherein the phase and frequency decoder is implemented by the main controller. 
     
     
       6. The system of  claim 1 , wherein the main controller computes the differences between the rotational frequency and phase for the first electric motor and the rotational frequency and phase for the second electric motor based on inputs from the phase and frequency decoder. 
     
     
       7. The system of  claim 1 , wherein the phase and frequency decoder computes the differences between the rotational frequency and phase for the first electric motor and the rotational frequency and phase for the second electric motor. 
     
     
       8. The system of  claim 7 , wherein the phase and frequency decoder outputs the differences between the rotational frequency and phase for the first electric motor and the rotational frequency to the first motor controller and the second motor controller. 
     
     
       9. The system of  claim 1 , wherein the main controller comprises:
 a processor coupled to a memory; 
 a steering control function executed by the processor, wherein the steering control function receives and interprets the steering control signal; 
 a track motor control function executed by the processor, wherein the track motor control function is configured to control the motor control signals to the first motor controller and the second motor controller in response to signals from the steering control function. 
 
     
     
       10. The system of  claim 9 , the main controller further comprising a frequency and phase difference processing function;
 wherein the steering control function receives frequency and phase information from the frequency and phase difference processing function and controls the track motor control function to produce the motor control signals. 
 
     
     
       11. A method for vehicle steering control of a track vehicle, the method comprising:
 receiving a steering control signal; 
 inputting a first rotation signal from a first rotation encoder representing a rotational frequency and phase of a first electric motor, the first electric motor coupled to a first continuous track mechanism; 
 inputting a second rotation signal from a second rotation encoder representing a rotational frequency and phase of a second electric motor, the second electric motor coupled to a second continuous track mechanism; and 
 outputting motor control signals to a first motor controller and a second motor controller in response to the steering control signal and monitored differences between the first rotation signal and the second rotation signal to drive the monitored differences below a threshold, wherein the first motor controller is coupled to the first electric motor and the second motor controller is coupled to the second electric motor. 
 
     
     
       12. The method of  claim 11 , further comprising:
 receiving via the steering control signal instructions to control the vehicle to travel straight; 
 processing the first rotation signal and the second rotation signal, to determine an error in motor frequency difference and motor phase difference; and 
 controlling a speed of one or both of first electric motor and the second electric motor to drive the error towards a minimum value. 
 
     
     
       13. The method of  claim 11 , further comprising:
 receiving via the steering control signal instructions to turn vehicle; 
 determining a turn angle from the steering control signal; 
 determining a current vehicle speed; 
 determining a target frequency difference based on the turn angle and the current vehicle speed; 
 executing a vehicle turn by controlling a difference in rotational speed of the first electric motor verses rotational speed of the second electric motor based on the target frequency difference; 
 processing the first rotation signal corresponding and the second rotation signal to determine a measured frequency difference between the first electric motor and the second electric motor; 
 determining a turn angle error based on a difference between the measured frequency difference and the target frequency difference; 
 controlling a speed of one or both of first electric motor and the second electric motor to drive the turn angle error towards a minimum value. 
 
     
     
       14. The method of  claim 13 , further comprising:
 determining a desired turn radius as a function of the turn angle and the current vehicle speed; and 
 determining the target frequency difference as a function of the desired turn radius and an absolute motor rotational frequency. 
 
     
     
       15. A vehicle steering control system for a track vehicle, the system comprising:
 a first continuous track drive sub-system positioned on a first side of a track vehicle, the first continuous track drive sub-system comprising: a first continuous track mechanism, a first electric motor coupled to the first continuous track mechanism, a first motor controller coupled to the first electric motor, and a first rotation encoder coupled to the first electric motor; 
 a second continuous track drive sub-system positioned on a second side of a track vehicle, the second continuous track drive sub-system comprising: a second continuous track mechanism aligned parallel to the first continuous track mechanism, a second electric motor coupled to the second continuous track mechanism, a second motor controller coupled to the second electric, and a second rotation encoder coupled to the second electric motor; 
 a main controller configured to input a steering control signal; and 
 a phase and frequency decoder coupled to the first rotation encoder and the second rotation encoder, wherein the phase and frequency decoder inputs a first rotation signal from the first rotation encoder representing a rotational frequency and phase of the first electric motor, wherein the phase and frequency decoder inputs a second rotation signal from the second rotation encoder representing a rotational frequency and phase of the second electric motor; 
 wherein the main controller outputs motor control signals to the first motor controller and the second motor controller in response to differences between the rotational frequency and phase for the first electric motor as represented by the first rotation signal and the rotational frequency and phase for the second electric motor as represented by the second rotation signal; 
 wherein when the main controller receives instructions to control the vehicle to travel straight based on the steering control signal, the main controller controls the first motor controller and the second motor controller to drive an error signal between the rotational frequency and phase of the first electric motor and the rotational frequency and phase of the second motor to a minimum value. 
 
     
     
       16. The system of  claim 15 , wherein the minimum value is defined as a value below a predetermined threshold. 
     
     
       17. A vehicle steering control system for a track vehicle, the system comprising:
 a first continuous track drive sub-system positioned on a first side of a track vehicle, the first continuous track drive sub-system comprising: a first continuous track mechanism, a first electric motor coupled to the first continuous track mechanism, a first motor controller coupled to the first electric motor, and a first rotation encoder coupled to the first electric motor; 
 a second continuous track drive sub-system positioned on a second side of a track vehicle, the second continuous track drive sub-system comprising: a second continuous track mechanism aligned parallel to the first continuous track mechanism, a second electric motor coupled to the second continuous track mechanism, a second motor controller coupled to the second electric, and a second rotation encoder coupled to the second electric motor; 
 a main controller configured to input a steering control signal; and 
 a phase and frequency decoder coupled to the first rotation encoder and the second rotation encoder, wherein the phase and frequency decoder inputs a first rotation signal from the first rotation encoder representing a rotational frequency and phase of the first electric motor, wherein the phase and frequency decoder inputs a second rotation signal from the second rotation encoder representing a rotational frequency and phase of the second electric motor; 
 wherein the main controller outputs motor control signals to the first motor controller and the second motor controller in response to differences between the rotational frequency and phase for the first electric motor as represented by the first rotation signal and the rotational frequency and phase for the second electric motor as represented by the second rotation signal; 
 wherein when the main controller receives instructions to control the vehicle to turn based on the steering control signals, the main controller controls the first motor controller and the second motor controller to drive a frequency difference between the first motor and the second motor to a target frequency difference. 
 
     
     
       18. The system of  claim 17 , where the main controller determines the target frequency difference as a function of a turn radius determined from the steering control signal and a speed of the vehicle. 
     
     
       19. The system of  claim 17 , where the main controller dynamically calculates the target frequency difference. 
     
     
       20. The system of  claim 17 , where the main controller obtains the target frequency difference from a table stored in a memory.